.ebenalexanderalmostdied four years ago. now, he has his book, "proof of heaven." >>reporter:ebenalexanderis a healthy, 58-year-old harvard-trained neurosurgeon. an expert of science. did you go to heaven? >> yes. >> reporter: four years ago, alexander nearly died from a massive brain infection that plunged him into a coma and shut down nearly his entire mind. he was barely alive in this world. but he says he journeyed elsewhere. >> i was rescued by this beautiful, spinning white light that had a melody. indescribable beautiful melody, that opened up in a bright valley. >> reporter: he says god was there, and a vast presence of infinite love. he met a young woman, he says, his guide as they soared on a butterfly wing. and she gave him a message from heaven. >> you are loved. you are cherished. there's nothing you have to fear. there's nothing you can do wrong. >> reporter: a lot of people are going to say, doctor, it was a hallucination. >> i know this was not a hallucination. not a dream. not what we call a confabulation. i know that it really occurred. and i know it occurred o